Temporal lobe epilepsy is characterized by seizures emanating from the temporal lobes, which sit on each side of the brain just above the ear. Previously, experts believed that the condition was related to isolated injuries of structures within the temporal lobe, like the hippocampus.
MP-RAGE volumes are segmented into 83 ROIs, which are further parcellated into 1000 cortical and 15 subcortical ROIs. Whole-brain white matter tractography is performed after voxelwise tensor calculation, and the density of fibers that connect each pair of cortical ROIs is used to calculate structural connectivity. T1w = T1-weighted.
Credit: Courtesy of Radiology and RSNA
But recent research has implicated the default mode network (DMN), the set of brain regions activated during task-free introspection and deactivated during goal-directed behavior. The DMN consists of several hubs that are more active during the resting state.
To learn more, researchers performed diffusion tensor imaging, a type of MRI that tracks the movement, or diffusion, of water in the brain's white matter, the nerve fibers that transmit signals throughout the brain. The study group consisted of 24 patients with left temporal lobe epilepsy who were slated for surgery to remove the site from where their seizures emanated. The researchers compared them with 24 healthy controls using an MRI protocol dedicated to finding white matter tracts with diffusion imaging at high resolution. The data was analyzed with a new technique that identifies and quantifies structural connections in the brain.
Patients with left temporal lobe epilepsy exhibited a decrease in long-range connectivity of 22 percent to 45 percent among areas of the DMN when compared with the healthy controls.
"Using diffusion MRI, we found alterations in the structural connectivity beyond the medial temporal lobe, especially in the default mode network," said Steven M. Stufflebeam, M.D., from the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital in Boston.
In addition to reduced long-range connectivity, the epileptic patients had an 85 percent to 270 percent increase in local connectivity within and beyond the DMN. The researchers believe this may be an adaptation to the loss of the long-range connections.
"The increase in local connections could represent a maladaptive mechanism by which overall neural connectivity is maintained despite the loss of connections through important hub areas," Dr. Stufflebeam said.
The results are supported by prior functional MRI studies that have shown decreased functional connectivity in DMN areas in temporal lobe epilepsy. Researchers are not certain if the structural changes cause the functional changes, or vice versa.
"It's probably a breakdown of myelin, which is the insulation of neurons, causing a slowdown in the propagation of information, but we don't know for sure," Dr. Stufflebeam said.
Dr. Stufflebeam and colleagues plan to continue their research, using structural and functional MRI with electroencephalography and magnetoencephalography to track diffusion changes and look at real-time brain activity.
"Our long-term goal is to see if we can we predict from diffusion studies who will respond to surgery and who will not," he said.
The study is part of the Human Connectome Project, a five-year project funded by the National Institutes of Health that uses neuroimaging techniques to study connectomics, or the functional and structural connections in the brain. Dr. Stufflebeam's colleague, Matthew N. DeSalvo, M.D., initiated the study as a medical student with the help of a 2013 Research Medical Student Grant from the Radiological Society of North America (RSNA).
"Altered Structural Connectome in Temporal Lobe Epilepsy." Collaborating with Drs. Stufflebeam and DeSalvo were Linda Douw, Ph.D., Naoaki Tanaka, M.D., Ph.D., and Claus Reinsberger, M.D., Ph.D.
Radiology is edited by Herbert Y. Kressel, M.D., Harvard Medical School, Boston, Mass., and owned and published by the Radiological Society of North America, Inc.
RSNA is an association of more than 53,000 radiologists, radiation oncologists, medical physicists and related scientists promoting excellence in patient care and health care delivery through education, research and technologic innovation. The Society is based in Oak Brook, Ill. (RSNA.org)
For patient-friendly information on MRI, visit RadiologyInfo.org.
Linda Brooks | EurekAlert!
Innovative genetic tests for children with developmental disorders and epilepsy
11.07.2018 | Christian-Albrechts-Universität zu Kiel
Oxygen loss in the coastal Baltic Sea is “unprecedentedly severe”
05.07.2018 | European Geosciences Union
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
13.07.2018 | Event News
13.07.2018 | Materials Sciences
13.07.2018 | Life Sciences